The present invention relates to the production and use of magnetic or magneto-optical memory disks. Broadly speaking, the present invention concerns improved slider constructions, such as burnishing heads or glide heads, which may be employed during the production of such disks. The present invention, however, is also more particularly directed to head gimbal assemblies and tests devices incorporating these improved slider constructions.
For years, magnetic disks have been employed in various types of data processing systems. A magnetic disk may be in the form of an auxiliary storage device such as a floppy disk, CD ROM, DVD, or the like, which is used to store and retrieve programs and data, or an arrangement of internal storage devices such as hard disks which are permanently enclosed in a drive compartment.
Generally, the hard disk drive within which rigid, magnetic memory disks are mounted is akin to a conventional record turntable in that there is a mechanism for rotating the disk and for translating a read/write data head across the surface of the disk to allow for access to a selected annular track. The magnetic disks are typically journaled for rotation about a spindle in a spaced relationship to one another. A tracking arm is associated with each disk and the data head is mounted to this tracking arm for accessing the desired information. These data heads are typically referred to as xe2x80x9cflyingxe2x80x9d data heads because they do not contact the surface of the disk during rotation. Rather, a data head hovers above the disk surface on an air bearing that is located between the disk and the head.
One concern during the production of rigid, magnetic memory disks is to ensure that asperities (i.e. protrusions on the surfaces of the disks) and particulate debris are adequately removed. Failure to do s o may cause an anomaly when an asperity is encountered by the data head during high speed revolutions, potentially causing errors in the transfer of information or even damage to the data head during operation. In an effort to reduce the occurrences of asperities, manufacturers commonly burnish the memory surfaces of the disks to remove the asperities. This is typically accomplished through the use of a particular head gimbal assembly known in the art as a burnishing head assembly. In the burnishing process, a burnishing head, sometimes more generally referred to as a slider, is mounted in a similar manner relative to the disk as discussed above. During the burnishing process, the burnishing head operates to polish these surface protrusions.
To further illustrate the burnishing process, reference is made to prior art FIG. 1 where a pair of burnishing head assemblies 10 and 12 are shown in use to remove asperities on opposite surfaces of a rigid magnetic memory disk 20 that is journaled for rotation about a spindle 26. While FIG. 1 only depicts the burnishing apparatus associated with a single rigid memory disk 20, it should be appreciated that a plurality of rigid memory disks may be rotatably journaled about spindle 26, with each of these memory disks having an associated pair of burnishing head assemblies. Each of burnishing head assemblies 10 and 12 includes an associated burnishing head, a flexure and a mounting structure that are adapted for use with a system for burnishing one of the moving surfaces of disk 20. Specifically, upper burnishing head assembly 10 has an associated mounting structure 11 to which is secured a flexure 13 and a slider in the form of a burnishing head 15. Burnishing head assembly 10 is employed to shave asperities and eliminate particulate debris on an upper surface 22 of disk 20. Similarly, lower burnishing head assembly 12 is employed to shave asperities and eliminate particulate debris on a lower surface 24 of disk 20, and lower burnishing head assembly 12 includes an associated mounting structure 14 to which is secured a flexure 16 and a slider in the form of a burnishing head 18.
In the past, alumina titanium carbide (AlTiC) has been the predominant composition by which burnishing heads are fabricated, and many burnishing heads additionally incorporate a diamond-like carbon (DLC) coating. Burnishing heads in the past have also been composed of aluminum oxide (Al2O3), as discussed in U.S. Pat. No. 4,330,910, issued May 25, 1982 to Schachl et al.
The next step in further refining magnetic disks once the burnishing operation is completed is through the use of a glide head. The purpose of a glide head is to detect, via proximately or contact, any remaining asperities which may come into contact with the data head during use. Glide heads hover and detect asperities which are located above specified data head flying heights. Glide heads, thus, dynamically test the integrity of surfaces of magnetic disk media.
For manufacturers to develop production quality rigid memory disks, it is necessary to utilize glide heads having more sensitive response characteristics. Unfortunately, many glide head assemblies have inherent problems associated with them because it is difficult to precisely control the electrical response characteristics of these devices. U.S. Pat. No. 5,689,064 to Kennedy, et al., issued Nov. 18, 1997, addresses this problem by providing, in part, a glide head assembly which incorporates a piezoelectric transducer disposed between a flexure and a slider in a cantilevered orientation. This problem is also addressed in U.S. Pat. No. 5,864,054 to Smith, Jr., issued Jan. 26, 1999, which discusses a legged piezoelectric transducer projecting from the side wall of a slider.
In any event, a glide head is also required to fly very close to the surface of a disk, at a flying height of less than 1 xcexc-inch (250 xc3x85), in order to effectively detect the presence of asperities which project above specified data head flying heights. It is, therefore, not uncommon for glide heads also to come into contact with asperities which have not been completely removed during the burnishing process.
Reference is now made to prior art FIG. 2 to illustrate the ability of a glide head assembly to detect the presence of asperities on disk 20 once the burnishing process is completed. A more detailed discussion of this phase in the manufacturing process may be found in either U.S. Pat. No. 5,689,064 or U.S. Pat. No. 5,864,054, the respective disclosures of which are incorporated herein by reference. In prior art FIG. 2, glide head assembly 30 is shown in use detecting the presence asperities on upper surface 22 of rigid magnetic memory disk 20. Although not shown, another glide head assembly could be employed in a similar fashion to detect asperities on the lower surface of disk 20. Glide head assembly 30 communicates detection results, via electrical leads 32 and paddleboard 34 to an appropriate processing system (not shown). Throughout the testing procedure, disk 20 rotates with a varying angular velocity xe2x80x9cwxe2x80x9d so that upper surface 22 passes beneath glide head assembly 30 with a constant linear velocity. As disk 20 rotates, glide head assembly 30 is moved inwardly in the direction xe2x80x9cRxe2x80x9d a selected speed so that the entire upper surface area of disk 20 passes therebelow.
The magnetic media industry, in particular, is requiring that magnetic recording disks have increasing recording densities. Commensurate with this is the need for burnishing heads and glide heads to hover at ever decreasing flying heights above a disk""s surface to produce flatter, smoother finishes on these rigid, magnetic disks. Currently, it is necessary to achieve a disk flatness between approximately 1.5 xcexcm and 10 xcexcm and a surface roughness (Ra) value that is between 3 and 12 Angstroms in order to keep up with industry demands. However, existing AlTiC sliders, whether burnishing heads or glide heads, are becoming a less viable solution during the production of rigid memory disks due to the relatively weak bond strength between the different materials. For example, AlTiC, which is a two-phase particulate composite material, has a relatively low fracture toughness in the range of 4 MPam0.5. This results in a tendency for the alumina and/or titanium carbide to break off during the burnishing process and become embedded in the disk. Not only does this decrease the efficiency of the slider itself, but it also jeopardizes the quality of the memory disk. Moreover, AlTiC has a Vicker""s hardness of approximately 20 GPa which means that, while this material may be relatively hard, it is difficult to machine. Due to the two phase nature of the material it is relatively difficult to obtain desired surface finishes during the manufacture of AlTiC sliders which increases production cost.
Accordingly, there remains a need to provide a new and useful slider construction for use with head gimbal assemblies in general, and burnishing head and glide head assemblies in particular, which does not exhibit the drawbacks discussed above that are associated with existing slider compositions. It would also be desirous to provide a head gimbal assembly and a test device which incorporates such an improved slider construction. The present invention is directed to meeting these needs.
It is an object of the present invention to provide a new and useful head gimbal assembly that is adapted for use during the production of magnetic memory disks.
Another object of the present invention is to provide a new and useful test device for use during the production of magnetic memory disks.
A further object of the present invention is to provide a new and useful slider as a component part of a head gimbal assembly, which head gimbal assembly may be either a burnishing head assembly, a glide head assembly or the like.
Yet another object of the present invention is to provide a slider which exhibits improved performance characteristics compared to existing slider constructions.
Still a further object of the present invention is to provide such a slider which is easier to machine and less expensive to manufacture.
In furtherance of these objectives, the present invention broadly relates to sliders, such as glide heads, burnishing heads, certifier heads, clock heads, data heads, or the like, which may be utilized in conjunction with rigid memory disks which may be either magnetic or magneto-optic. To this end, it should be appreciated that the particular type of slider would be utilized either in the testing phase of manufacturing recording media or during recording applications pertinent in the magnetic recording head industry. As will be appreciated from the description to follow, the present invention also more particular concerns either a head gimbal assembly or a test device incorporating the improved slider construction.
Broadly then, the present invention provides for a slider adapted for use with a system that includes a mounting structure, a flexure attached thereto, and a rotary drive. The slider comprises a rigid body adapted to be suspended from the flexure to define a mounted state. This body is fabricated from a single phase material and includes an air bearing surface operative to be oriented in facing relationship to a moving surface of the memory disk when in the mounted state. A mounting surface is positioned opposite the air bearing surface and a sidewall extends between these two surfaces. It should be appreciated that the slider may take on a variety of different shape configurations known to those in the art depending on its particular application.
Preferably, the single phase material has one or more desirable properties, such as a grain size less than 1.5 microns, a surface roughness (Ra) value less than 10 Angstroms (xc3x85) (as may be measured by means of an appropriate optical profilometer), a fracture toughness greater than 4 MPam0.5 (as may be measured by the Chantikul identation method discussed in the Journal of the American Ceramics Society, p. 64(9), 1981, pp.539-44), a Young""s modulus less than 300 GPa, and a porosity of less than xc2xd%. Such a porosity can be achieved by hot isostatic pressing or hot pressing. The single phase material is preferably in the form of zirconium oxide (ZrO2), also known as zirconia. The zirconium oxide may have a fracture toughness of about 7 MPam0.5 and a Young""s modulus of approximately 215 GPa. It is also preferred that the zirconium oxide has a crystal structure that is substantially tetragonal. The zirconium oxide may be partially stabilized using a selected doping agent in the form of a metal oxide, such as yttrium oxide (Y2O3), cerium oxide (CeO2), scandium oxide (Sc2O3), magnesium oxide (MgO), calcium oxide (CaO), other known rare earth oxide stabilizers, or a mixture thereof. Where yttrium oxide is employed as the doping agent, it is preferred to dope the zirconium oxide with 2.5-5 mol % Y2O3. Zirconias with  less than 2.5 mol % Y2O3 is tough, but less stable. On the other hand, zirconias with  greater than 5 mol % Y2O3 is stable, but not tough enough. Zirconium oxides having these characteristics are discussed in U.S. Pat. No. 5,820,960 issued Oct. 13, 1998 to Kwon, U.S. Pat. No. 5,824,386 issued Oct. 20, 1998 to Kwon, et al., and U.S. Pat. No. 5,916,655 issued Jun. 29, 1999 to Kwon. The respective disclosures of these patents are incorporated herein by reference. The zirconium oxide can be polished to the surface finish (Ra) of  less than 10 xc3x85, and it is expected that the surface roughness of the air bearing surface will be as low as  less than 2 xc3x85 in the future in order to achieve rapidly increasing storage density goals.
The present invention also relates to a head gimbal assembly adapted for use with a system during production of rigid memory disks. Here, the head gimbal assembly comprises a flexure extending along a longitudinal axis, with the flexure including a proximal end portion adapted to be secured to a support structure and a distal end portion adapted to be positioned in proximity to a moving surface of the rigid memory disk. A slider is secured to the distal end portion, with this slider having one or more of the characteristics discussed herein.
Finally, a test device is provided for testing moving surfaces on a rotating disk to determine a presence of asperities thereon. The test device broadly comprises a support structure, a rotary drive, at least one glide head assembly, signal processing electronics and electrical interconnects. The rotary drive is operative to rotate a disk thereon relative to the support structure. The glide head assembly is supported on the support structure and includes a flexure and slider as discussed herein, and a piezoelectric transducer supported on the slider. The piezoelectric transducer is responsive to the presence of an asperity relative to the slider as the asperity moves past the slider to vibrate, thereby to produce an electronic signal. The signal processing electronics are operative to process this electronic signal, and the electrical interconnects establish communication between the transducer and the signal processing electronics.